Potomac & Anacostia Rivers

Flood Inundation Mapping Tool Washington, D.C., and Vicinity

Webinar

Moderator: Nick Bonard, National Capital Planning Commission

November 29, 2016

Agenda

Overview of Flood Inundation Mapping Tool Project Stacey Underwood, Silver Jackets Coordinator and Project Manager, U.S.

Army Corps of Engineers

Demonstration of Flood Inundation Mapping Tool Jason Elliott, Senior Service Hydrologist, National Weather Service

Question & Answer

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“All Moderators”

Potomac & Anacostia Rivers

FIM Overview Presented by Stacey Underwood, Silver Jackets Coordinator and Project Manager,

U.S. Army Corps of Engineers, Baltimore District

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DC FIM Project Partners

Project conducted by members of DC Silver Jackets Team:

Local

District of Columbia; Led by DOEE

City of Alexandria; Fairfax and Arlington counties, VA

Prince George’s County, MD

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DC Flood History

There are three types of flooding that can impact low areas of

the city: 1) riverine 2) tidal/coastal storm surge 3) interior

flooding

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Major riverine floods have

occurred in 1936, 1937,

1942 and two in 1996

Major tidal floods have

occurred in 1933, 1972

(Agnes), and 2003 (Isabel)

Most notable interior

flooding was June 2006

Washington Navy Yard, 1936

Constitution Ave, NW, June 2006

DC FIM Project Overview

New on-line maps allow government leaders, emergency

managers, and the public to view the extent and depth of

expected riverine or tidal flooding based on NWS forecasts

NWS projects the flood levels at USGS water gauges and the

Corps’ hydrologic and hydraulic models and maps display

where the flooding could occur and how deep it may be

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DC FIM Project Overview

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DC FIM Technical Aspects

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Ground Elevation=

5.0 ft. NAVD 88

Predicted Flood Elevation=

10.0 ft. NAVD 88

DEPTH GRID VALUE

= 5.0 FEET

Normal Tide

DC Area Gauges

Forecast Points:

- Potomac River at

Georgetown

- Washington Channel at SW

Waterfront

- Potomac River at Alexandria

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Flood Inundation Areas for 3 Gauges

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Potomac River at Georgetown

Washington Channel at SW

Waterfront

Potomac River at Alexandria

DC FIM Technical Aspects

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TIDAL/STORM SURGE

Fletcher’s

Cove

Fort Hunt Broad Creek

NY Ave.

• 14 miles along Potomac River

• 10 miles along Anacostia River

• Flood maps extend up

tributaries such as Four Mile

Run, Cameron Run and Oxon

Run

Fort Hunt Broad Creek

Fletcher’s

Cove

DC FIM Technical Aspects

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RIVERINE

NY Ave.

• Same flood map areas as tidal

maps

• Maps show riverine flooding down

the Potomac River and water

backing up the Anacostia River

and other tributaries

DC FIM – Benefits

• Decisions on evacuations, road closures, power grid shut

down, implementing flood risk management measures,

moving vehicles to higher ground, moving valuables to higher

levels, etc.

• To view various flood levels and see impact to region

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17th Street Levee Closure

DC FIM – Considerations/Limitations

• Do not depict interior flooding

• Assume high tide for riverine flooding

• Maps include Potomac Park Levee System. Other local and federal flood risk management systems not shown - (Blue Plains, Georgetown Waterfront, Joint Base Anacostia Bolling, etc.)

• Used ground elevation below elevated roadways as basis - elevated roadways may be shown as flooded when they are not

• Maps do not reflect concurrent significant riverine and storm surge flooding, but this is a highly rare and unusual occurrence

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Demonstration of Mapping Tool

by Jason Elliott

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http://www.weather.gov/washington/PotomacInundationMaps